Nematic coherence optics

Application of Nematic Liquid Crystals in Coherence Optics 153... 

In this section, we discuss a mechanism for enhanced optical nonlinearity in which the photoinduced charges and fields occur within the liquid crystal. It is well known that dc field induced cmient flow in nematic liquid crystals, which possess anisotropic conductivities, could lead to nematic flows and director axis reorientation, and to the creation of a space-charge field. The charged carriers responsible for the electrical conduction come from impurities present in the otherwise purely dielectric nematic liquid crystal. If these impurities are photoionizable, an incident optical intensity [e g., an intensity grating created by the interference of two coherent optical beams (see Fig. 8.13)], it is possible, therefore, to create a space-charge... 

Both CdS and a-Si have been successfully used as the photocondoctor 45°-twisted nematic layers and, on an experimental basis, ferroelectric layers have been used for the liquid crystal. CCD structures and silicon vidicon microdiode arrays have been used in place of the photocon-ductive layer. The device is useful both when the write beam is coherent (for example, a scanned laser) and when it is incoherent (for example, a CRT). In the latter case, the SLM can be used as an incoherent-to-coherent converter. The CRT-written device has also found application as a projection display. There exists a very large potential market for optically addressed SLMs in a variety of optical processing applications and for projection displays. 

To conclude this section on 2D NMR of liquid crystals, some studies of more exotic liquid crystalline systems are pointed out. Polymer dispersed nematic liquid crystals have attracted much attention because of their applications as optical display panels. Deuteron 2D quadrupole echo experiments have been reported [9.28] in the isotropic and nematic phases of / -deuterated 5CB dispersed in polymers. A similar technique was used [9.29] to study two model bilayer membranes. Both studies allow determination of the lineshape F(u ) due to quadrupolar interactions and the homogeneous linewidth L(u ) of the individual lines [9.28]. The 2D quadrupole echo experiment has also been used [9.30] to separate chemical shift and quadrupolar splitting information of a perdeuterated solute dissolved in a lyotropic liquid crystal. The method was compared with the multiple-quantum spectroscopy that is based on the observation of double-quantum coherence whose evolution depends on the chemical shift but not on the quadrupolar splitting. The multiple-quantum method was found to give a substantial chemical shift resolution. The pulse sequences for these methods and their treatment using density matrix formalism were summarized [9.30] for a spin 1=1 system with non-zero chemical shift. Finally, 2D deuteron exchange NMR was used [9.31] to study ring inversion of solutes in liquid crystalline solvents. 

Numerical aperture Nematic liquid crystal Optical coherent tomography Optical parametric amplifier Optical parametric oscillator Photo multiplier tube Nonlinear polarization Picosecond... 

Strong scattering of light. Similar to the phonon collective excitations in 3D solids, orientational normal modes in liquid crystals can be considered as plane-wave-like, spatially coherent excitations of the director field n (r, f), which determines the mean orientation of the long molecular axis. In contrast to phonons in solids, the excitations in liquid crystals are always overdamped because of the viscosity. De Gennes [27] considered the effect of such a thermally excited and overdamped orientational plane wave dnir,t) = 5n (t) on the optical properties of nematic and found that it is directly reflected in the fluctuation of the dielectric tensor field 5e(r, t) ... 

Pahalov, V. B., Tumisian, A. S. Chilingarian, Y. B. (1980). Self focusing of Ught in the nematic phase of liquid crystal MBBA. Proc. Itf National Conference on Coherent and Non-linear Optics. Kiev 1980. 

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